Various catalytic dehydrogenation processes for hydrocarbons are known by which less saturation and more reactive compounds are produced. Temperature control in dehydrogenation reactions of this type is considered crucial since the reactions are highly endothermic reactions which require closely controlled and relatively high temperatures for favorable equilibria, as well as for adequate reaction velocities. Reaction temperature control in these processes has been generally accomplished by maintaining a desired average temperature of the catalyst bed.
Active dehydrogenation catalysts employed in fixed-bed, fired-tube reactors, are usually employed in commercial operations for producing isobutene from isobutane. For example, it is known to commercially dehydrogenate light aliphatic hydrocarbons, such as isobutane, in the presence of catalysts which comprise a Group II metal aluminate, a Group IVA metal oxide, and a Group VIII metal.
It is also known in the art that the activity of such dehydrogenation catalysts will decline to an ineffective level after a period of about 6 hours to about 20 hours of continuous use. The decline in dehydrogenation catalyst activity is believed to be due to the formation of coke and polymers on the catalyst. In order to maintain catalyst activity, it has therefore been necessary to periodically regenerate the catalyst. This is usually done by cutting off the feed to the spent catalyst, and then treating the spent catalyst with a feed gas containing oxygen and steam. Therefore production of the reactor is suspended during the regeneration period.
A primary object of this invention is to increase production of isobutene from isobutane in a dehydrogenation reactor by compensating for the decline of catalyst activity.
It is a more specific object of this invention to compensate for the decline in catalyst activity during continuous use of the catalyst in a dehydrogenation reactor by applying a more effective temperature control scheme.
It is a further object of the invention to provide an improvement for a hydrocarbon dehydrogenation process which is safe, simple, effective, efficient and economical.